Here’s a low cost solution I adopted. I can’t take credit for the idea since I got the basic idea from a youtube video several years ago. My addition to the original is the lever that releases both clamps at the same time. This is handy since I keep it completely closed when its not in use. I could pull it off and take more picts of the release mechanism, but its basically just a hinge, angle iron, and some screws. The clamping boards are poplar lined with cork. The other wood parts were just scrap lumber. To use it, I pull the release lever and pull out the outer clamp board. I drop the guitar in until it rests on the ledge. This puts the bridge just above the top of the inner clamp board. Then I push the outer clamp board in until it touches the guitar body. Then I use the pipe clamp screws to put just enough pressure on the body to keep it from moving. No more having to hold the guitar upright while doing sand paper pulls.